Accompanying an increasing trend toward blue laser DVD drives, a high gain and a wide band are demanded as characteristics of a transimpedance amplifier that forms a light-receiving amplifier circuit.
In a transimpedance amplifier shown in FIG. 10, which uses a parallel connection circuit formed of a resistance and a capacitance as a feedback circuit unit, a extreme frequency can be indicated by 1/(2π×resistance×capacitance).
In order to broaden a band of the transimpedance amplifier, the resistance or the capacitance that forms the parallel connection circuit, for example, should be reduced.
However, when the resistance is reduced, a gain of the transimpedance amplifier is reduced, which is not desirable. Thus, the capacitance should be reduced. However, another problem of peaking shown in FIG. 11, in which the gain abruptly increases with respect to a frequency, may arise. When such peaking occurs, although the band may be broadened on one hand, a group delay deteriorates in a region of the frequency at which the peaking has occurred. Thus, it is not desirable to reduce the capacitance.
As another means for broadening the band, a feedback circuit shown in FIG. 12 is disclosed in Patent Document 1, for example. In this feedback circuit, a parallel connection circuit formed of a resistance and a capacitance is connected in series to a parallel connection circuit formed of a resistance and a capacitance. However, in the case of this configuration as well, a problem similar to that in the conventional art described before may arise.
Patent Document 1 further discloses a circuit shown in FIG. 13, at the same time. In this feedback circuit, a parallel connection circuit formed of a resistance and a capacitance and a parallel connection circuit formed of a resistance and a capacitance are connected in series, and between the ground and a connecting point between the parallel connection circuits, a capacitance is connected.
Patent Document 1:
JP Patent Kokai Publication No. JP-P-2000-315922A